Phthalocyanine dyes are widely explored for use in such diverse applications as textile colorants (Christie, R. M. Colour Chemistry, Royal Society of Chemistry: Cambridge, UK, 2001), nonlinear optical generation and limiting (de la Tone, G. et al., J. Mater. Chem. 1998, 8, 1671-1683; Calvete, M. et al., Synth. Met. 2004, 141, 231-243), photodynamic therapy (Allen, C. M. et al., J. Porphyrins Phthalocyanines 2001, 5, 161-169), photovoltaics (Nazeeruddin, M. et al., J. Porphyrins Phthalocyanines 1999, 3, 230-237; Petritsch, K. et al., Synth. Met. 1999, 102, 1776-1777), sensors (Zhou, R. et al., Appl. Organomet. Chem. 1996, 10, 557-577), electrochromic displays (Jiang, J. et al., In Supramolecular Photosensitive and Electroactive Materials, Nalwa, H. S. Ed., Academic Press: San Diego, Calif., 2001, 188-189), and information storage (Li, J. et al., J. Org. Chem. 2000, 65, 7379-7390; Gryko, et al., J. Mater. Chem. 2001, 11, 1162-1180; Gross, T. et al., Inorg. Chem. 2001, 40, 4762-4774; Schweikart, K.-H. et al., J. Mater. Chem. 2002, 12, 808-828; Schweikart, K.-H. et al., Inorg. Chem. 2003, 42, 7431-7446; Wei, L. et al., J. Org. Chem. 2004, 69, 1461-1469)
In molecular electronics, ordered phthalocyanine materials are generally sought over disordered materials, and the routes to ordered materials can vary widely from sublimation of phthalocyanines into crystalline layers, Langmuir-Blodgett film formation, mesomorphism, and backbone polymerization (Achar, B. N. et al., J. Polym. Sci. Polym. Chem. Ed. 1982, 20, 1785-1790; Venkatachalam, S. et al., J. Polym. Sci. Part B 1994, 32, 37-52; Gürek, A. G. et al., J. Porphyrins Phthalocyanines 1997, 1, 67-76; Gürek, A. G.; Bekaroglu, O. J. Porphyrins Phthalocyanines 1997, 1, 227-237; Wörhle, D. et al., J. Porphyrins Phthalocyanines 2000, 4, 491-497; Kingsborough, R. P.; Swager, T. M. Angew. Chem. Int. Ed. 2000, 39, 2897-2900).
Backbone polymerization of phthalocyanines is distinguished from the axially connected or “shish-kebab” phthalocyanines (Hanack, M. et al., In Handbook of Conducting Polymers, Skotheim, T. A., Elsenbaumer, R. L., and Reynolds, J. R., Eds., Marcel Dekker, New York, 1998, 381). Backbone polymerization of phthalocyanines is difficult, owing partly to the limited solubility of most phthalocyanines and partly to limitations of the geometry of phthalocyanines. The advantages of backbone polymers of phthalocyanines relative to non-covalently assembled phthalocyanines are (1) improved thermal and chemical stability of the short and long range structure, (2) reproducible preparation of materials without the use of expensive or delicate instrumentation, and sometimes (3) the addition of through-bond mechanisms of electronic communication between the component monomers as a complement to through-space mechanisms of energy transfer and/or conductivity.
Most efforts at preparing phthalocyanine polymers have utilized the phthalocyanine macrocyclization reaction as the material-forming step, with bridged or bilateral building blocks such as 1,2,4,5-tetracyanobenzene or dicyanobenzenes linked by alkyl chains or other intermediary groups. This strategy typically results in two-dimensional sheets of fused or linked pigments. Another approach is to prepare oligomers of fused phthalocyanines with polymerizable end groups, which also gives two-dimensional products. The ladder oligomers prepared by Hanack and coworkers are the best example of a linear one dimensional phthalocyanine material (Hauschel, B. et al., J. Chem. Soc., Chem. Commun. 1995, 2449-2451; Hanack, M.; Stihler, P. Eur. J. Org. Chem. 2000, 303-311). However, the stepwise synthesis used for such oligomers is not well suited to the preparation of polymers bearing many phthalocyanine macrocycles. Kingsborough and Swager prepared a thiophene-linked metallophthalocyanine polymer via electropolymerization of thiophene end groups. The resulting material is described as “nearly linear”, but this polymer allows for rotation of the phthalocyanines and is not likely to be shape-persistent. The electroactive linking groups play a large role in the character of the resulting polymer. The fused linkages in the ladder oligomers and the phthalocyanine sheets also have a significant effect on the photochemical and electrochemical properties of the individual chromophores of the resulting material. In many cases this perturbation may be beneficial and intentional. However, these perturbation effects are not easily predicted and therefore complicate the design of electronic materials. Accordingly, there is a need for new compounds and methods for preparing linear (non-fused) materials.